Tesla's Battery Evolution: 4680 vs 2170 Cell Comparison

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Manufacturing

Cost Analysis

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Introduction to Monroe Live and Focus on Costing in Automotive Benchmarking

Monroe Associates is an engineering consulting firm specializing in competitive benchmarking in automotive and other industries, costing, and design optimization.
The episode will focus on the costing aspect of automotive benchmarking, specifically comparing the 4680 and 2170 battery packs in terms of architecture, assembly, design, and cost.
The 2170 and 4680 refer to the form factor of the battery cell, not model numbers.
The 2170 cell has a diameter of 21mm and a length of 70mm, while the 4680 cell is larger with a diameter of 46mm and a height of 80mm.
The episode will compare the 2020 model year 2170 battery pack with a capacity of 75 kilowatt hours to the 2022 model year 4680 battery pack with a capacity of approximately 67 kilowatt hours.
The episode is sponsored by Joah, a provider of Tesla accessories, including all-weather floor liners, center console organizers, armrest organizers, custom car fragrances, and umbrellas.
The 2170 cells are purchased by Tesla from Panasonic and installed into the traditional 2170 model y battery pack, while the 4680 battery pack is a new form factor.

Advantages of In-house Manufacturing for Tesla's Battery Components

In-house manufacturing eliminates the markup associated with purchasing components from suppliers.
Cost savings can accumulate quickly, especially considering the large number of cells used in Tesla's battery packs.
Manufacturing components in-house requires core competency and significant capital expenditure.
Larger cells can reduce assembly time and increase gravimetric energy density.
The amount of can material per pack does not significantly differ between the 2170 and 4680 cells.

Structural Design Comparison: 2170 Model Y vs 4680 Model

The 2170 Model Y battery pack has a stamped aluminum tray with extrusions running longitudinally, a coated steel lid, and a Power Electronics Penthouse placed on top.
The modules in the 2170 Model Y are built with 2170 cells, extruded aluminum cooling lines, and a silicone-based potting material for thermal isolation.
The module structure is provided by injection molded side rails with compression limiters, anchored with threaded fasteners to the battery pack chassis.
The 2170 Model Y battery pack is closed on the top with injection molded cover panels and has potting and wire bonding exposed on the bottom.
The whole pack is decked upward into the vehicle with a series of fasteners around the side sills and mid-pack fasteners to mitigate relative motion and noise.
In contrast, the 4680 Model battery pack is a large deep drawn bathtub with no extrusions or structure.
The 4680 Model uses cell arrays instead of traditional modules, with wood pieces supporting plexiglass for display purposes.
The 4680 Model has a simpler design with cell arrays set into the stamped tub structure.

Battery Pack Structure and Assembly of Tesla 4680 Cells

Tesla's 4680 battery pack does not have injection molded side rails or an enclosure.
The cells are assembled using a Bandelier assembly method, with 69 cells glued onto extruded cooling lines.
Cells are combined in batches of three, placed in a tray, and have their current collectors welded.
The bottom of the assembly has an injection molded polycarbonate support structure with a void space and a mica sheet.
The entire assembly is set into a bathtub-like structure using a robotic arm, with no fasteners required.
Pink polyurethane foam is used to structurally anchor the cells and fill the space between the assembly and the lid.
The foam expands and cures to form a rigid structure, making contact with the entire interior surface area of the lid.
The cells are suspended from the underside of the lid and tied in at the front and rear of the vehicle.
High durometer polyurethane foam molding is used on the sides to create a crush space for side impacts.

Design and Assembly Considerations for Battery Packs in Vehicles

The choice of material for filling void spaces in battery packs affects cost and compliance.
Compliance is important for absorbing impact during side collisions.
The thickness of the battery pack is increased when injection molded structures are not used, to ensure no damage during normal loading.
Initial designs often prioritize safety over cost optimization, but later iterations can focus on cost reduction.
The 4680 cell design may have a more conservative factor of safety, which could be optimized in future versions.
Fasteners are used to attach the battery pack to the vehicle, with slight differences between the 2170 and 4680 packs.
The 4680 pack does not have a separate floor pan; the pack lid serves as the vehicle floor.
The battery pack lid is made of stamped steel coated with an aluminum cover for the onboard charger and Power Electronics.

Explanation of the Design and Functionality of the Battery Pack Lid

The pads on the battery pack lid help reduce oil canning and NVH (noise, vibration, and harshness) by damping relative motion between the lid and the floor pan.
The lid is made of laser welded blank, which allows for varying thickness in different areas of the lid for cost and weight optimization.
The thickness is thickest towards the front for front impact considerations and load-bearing purposes.
The mid pack area has a slightly thinner thickness and supports the structure for seat risers and the center console.
The thickness is slightly increased towards the rear of the lid.
The use of laser welded blank optimizes cost and weight for steel components in EVs.
The battery pack lid serves as the floor pan and closes off the cabin compartment.
The lid forms a seal with the body structure to ensure a secure and sealed cabin.
A closed cell polyurethane seal is used around the perimeter of the battery pack lid to mate with different sections of the Giga castings and stamped body side components.

Comparison of Battery Pack Structures in 2170 and 4680 Model Vehicles

The 2170 model has a slightly different extruded rubber seal compared to the 4680 model, which helps prevent water leaks.
The 4680 pack is designed to seal the cabin as well as the battery pack, ensuring the safety of occupants.
Quality issues are being worked out in the seal of the 4680 pack, which is a long and large perimeter that needs a good seal in every aspect.
The lid structure of the 4680 pack has a more flat profile, while the 2170 pack has a deeper tray that tapers down.
The mating point of the 2170 pack is lower on the side sills, allowing the battery pack to step up into the cabin space.
The floor height between the two vehicles is the same, despite the different pack configurations.
The available legroom and comfort in the cabin is not affected by the type of battery pack used.

Available Reports on Tesla Battery Pack Tear Down

Report compares the 4680 Model Y pack and the 2170 Model Y pack in terms of mass and cost.
Quantifies differences between major subsystems such as module design, current collectors, and intrapac thermal management.
Includes photos from the tear down and CAD models of the battery pack.
Full vehicle report available, comparing Giga castings and stamped components.
Reports can be obtained by contacting sales@leandesign.com.

Comparison of 2170 and 4680 Battery Packs in Tesla Vehicles

Monroe Associates specializes in competitive benchmarking and will focus on costing in automotive benchmarking.
The episode compares the 2170 and 4680 battery packs in terms of architecture, assembly, design, and cost.
The 2170 cell has a diameter of 21mm and a length of 70mm, while the 4680 cell is larger with a diameter of 46mm and a height of 80mm.
The episode compares the 2020 model year 2170 battery pack with a capacity of 75 kilowatt hours to the 2022 model year 4680 battery pack with a capacity of approximately 67 kilowatt hours.
The 2170 cells are purchased from Panasonic and installed into the traditional 2170 Model Y battery pack, while the 4680 battery pack is a new form factor.
In-house manufacturing eliminates supplier markups and can lead to cost savings.
Larger cells can reduce assembly time and increase energy density.
The 2170 Model Y battery pack has a stamped aluminum tray, extruded aluminum cooling lines, and injection molded side rails.
The 4680 Model battery pack is a large deep-drawn bathtub with no extrusions or structure, and it uses cell arrays instead of traditional modules.
The assembly method for the 4680 pack involves gluing cells onto extruded cooling lines and using polyurethane foam to anchor the cells and fill void spaces.

Battery Pack Lid Design and Sealing in EVs

Pads on the battery pack lid reduce oil canning and NVH.
Laser welded blank allows for varying thickness in different areas for cost and weight optimization.
Thickness is thickest towards the front for front impact considerations.
Mid pack area has slightly thinner thickness for seat risers and center console support.
Thickness is slightly increased towards the rear of the lid.
Laser welded blank optimizes cost and weight for steel components in EVs.
Battery pack lid serves as the floor pan and closes off the cabin compartment.
Lid forms a seal with the body structure to ensure a secure and sealed cabin.
Closed cell polyurethane seal is used around the perimeter of the battery pack lid.